> On Oct 31, 2016, at 2:58 PM, jim stephens <jwsm...@jwsss.com> wrote:
>
> If you cared about not erasing the drive manufacture's data on sealed media
> Winchester and the like you have to avoid any writes to cylinder 0 at all.
>
> The drive formatting software could read that cylinder track 0 for a defect
> map. Nothing to stop you from overwriting it, but you would then need to do
> a local media certification that is more complicated than just formatting the
> drive, and mapping out defective tracks / sectors.
>
> I never worked with a system that had a controller or software that could
> read the defect track, so don't know how that was used. Later drives with
> more intelligence in the drive are another matter, but in those cases, the
> hiding of the defect data can be a task assigned to that processor, and don't
> need magic handling of the addressing.
I haven't seen drives that put the defect data on track 0. DEC put it at the
very end of the drive (see DEC Std 144). And as I recall, CDC did likewise in
the 844 drives (RP04 lookalikes). As for software using that data, RSTS
certainly did.
paul
